Fuel injection pump after injection control apparatus



Sept. 10, 1968 L. HIDEG I 3,400,662

FUEL INJECTION PUMP AFTER INJECTION CONTROL APPARATUS Filed March 24, 1967 INVENT R.

Ill 4452/0 //i cry.

United States Patent 3,400,662 FUEL INJECTION PUMP AFTER INJECTION CONTROL APPARATUS Laszlo Hideg, Dearborn Heights, Mich, assignor to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Filed Mar. 24, 1967, Ser. No. 625,726 Claims. (Cl. 1032) ABSTRACT OF THE DISCLOSURE A fuel injection pump having a central rotatable fuel flow metering shaft that is movable axially in one direction by the vehicle accelerator pedal linkage, and in the opposite direction by a speed responsive governor, to control the initial injection and duration of injection of fuel; the metering shaft having a channel that spills a finite volume of fuel back into the pump plunger cavities after injection is. terminated, to reduce the residual pressure in the injection line.

This invention relates, in general, to a fuel injection pump. More particularly, it relates to one in which the conventional separate volume-retraction type delivery valves are eliminated by their function being incorporated as an integral part of the fuel metering shaft assembly.

Specifically, the invention is an improvement on the fuel injection pump assembly shown and described in Patent No. 3,319,568, Louis L. Repko et al., filed July 16, 1965, having a common assignee. The latter fuel injection pump has a central fuel injection system including a metering shaft that cooperates with individual fuel injection lines in which the residual pressure is controlled by separate volume-retraction type delivery valves. In a system of the latter type, delivery valves are desirable to prevent after injection, etc., fuel loss, and increase of unburned hydrocarbon concentration in the exhaust gas, in a known manner. Each of the volume retraction valve units, however, usually requires a housing, a moving valve body, and a valve spring, which requires close production tolerances.

The invention achieves volume retraction from the injection line of multi-plunger rotary valve type injection pumps without the use of separate valve units, and thereby reduces the cost of the pump assembly and the number of parts. The invention accomplishes the above by utilizing metered portions of the intake stroke of the injection plungers to retract the quantity of fuel necessary to reduce the residual pressure in the injection line.

It is an object of the invention, therefore, to provide a fuel injection pump assembly of the central metering type with built-in means to provide injection line volume retraction without the use of a separate delivery valve for each line.

It is a further object of the invention to provide a central metering shaft type injection pump assembly with fuel volume retraction channels in the shaft that each progressively and individually connect the individual pump plunger fuel chambers to individual fuel injection lines to retract a finite volume of the fuel from the line into the plunger cavity during a portion of the intake stroke of the plunger, to reduce the injection line residual fuel pressure.

-It is a further object of the invention to provide a fuel injection pump assembly of the type described above in which the volume retraction fuel is utilized to balance the side load exerted on the bore by the fuel to be injected and contained in the metering shaft channels.

It is a still further object of the invention to provide a fuel injection pump assembly that is economical to manufacture and has fewer parts than a conventional central metering type shaft pump that includes separate delivery valves for each injection line, the pump of the invention eliminating the separate delivery valves by integrally incorporating their functions into the metering shaft and bore assembly.

Other objects, features and advantages of the invention will become apparent upon reference to the succeeding detailed description thereof, and to the drawing, wherein the single figure illustrates, schematically, a cross sectional view of a fuel injection pump assembly embodying the invention.

As stated above, the figure shows schematically, a cross section of a fuel injection pump assembly, that, for the most part, may be conventional, and similar to that shown and described in Patent No. 3,319,568. In general, the pump is enclosed in a stationary housing 10 having lower, central, and upper portions 12, 14 and 16, repsectively, that are interconnected by any suitable means, not shown. Portion 14 has a central bore 18 in which a metering shaft 20 is rotatably and axially slidably mounted. The shaft has lower and upper portions 22 and 24 that extend into or through housing portions 12 and 16, as shown. Lower portion 22 is adapted to be connected to a portion of an internal combustion engine to be driven thereby in a clockwise direction, for example, by any suitable means, not shown. The central portion of the metering shaft 20 is vertically aligned and guided axially by the walls of bore 18, and is rotatably mounted on side bearings 26 secured in housing portion 14.

A known type of swash plate 30 is fixedly secured to shaft portion 22 and is rotatably mounted on bearing means 32. The swash plate has -a cam surface 34 that is engaged by a number (only two shown) of pump plungers 36, which, in this case, preferably is eight to correspond to the cylinders of a multibank, V-8 engine. Plungers 36 are cumferentially spaced, and reciprocally mounted in bores 38. Each of bores 38 at its upper end is integral with an enlarged diameter chamber or cavity 40 that is connected radially by a metering hole or line 42 to metering shaft bore 18. The opposite radial portion of chamber 40 has an access hole 44 that is closed by a plug 46.

The eight metering holes 42, in this case, would be circumferentially spaced, as shown, and in the same radial plane for individual cooperation with a fuel flow channel in the metering shaft, to be described later.

Axially spaced from metering holes 42 are an equal number of injection line holes or ports 48 that also are circumferentially spaced and axially aligned in the same manner as metering holes 42. The injection line ports in this case all open at one end into bore 18, and at their opposite ends are each connected individually to one of eight (only two shown) fuel injection lines 50. The injection lines are each sealingly connected into the housing by suitable adapters 52. Each of the injection lines 50 would contain a nozzle assembly, not shown, of a known type that would be spring closed below a predetermined fuel pressure in the line. This terminates fuel injection when the fuel supply is cut off at the injection line holes or ports 48, in a known manner.

Metering shaft '20 is provided, at its upper end, in housing portion 16, with an engine driven governor assembly 54. The governor may be of a known construction, such as that shown in Patent No. 3,319,568. It is fixed to the metering shaft in such a manner that increases in the speed or rotation of the metering shaft cause an outward arcuate movement of a pair of flyweight members 56 to pivot arm portions 58 downwardly against a thrust bearing 59 fixed on the metering shaft. This moves the shaft axially in the same direction to thereby vary the axial position of the shafe relative to the spill or metering holes 42, and injection line holes 48.

A pivotally mounted fuel regulator lever 60, which is connected by suitable linkage, not shown, to the conventional vehicle accelerator pedal, is connected pivotally at 61 to the top portion of the metering shaft. The position shown for lever 60 in this case would correspond to a closed throttle or engine idle speed position of the accelerator pedal. Depression of the pedal from this latter position rotates lever 60 counterclockwise against the force of a return spring (not shown) and, accordingly, raises metering shaft in an axial direction.

As thus far described, therefore, in general, metering shaft is operatively driven by the engine and rotates swash plate to alternately and progressively reciprocate the individual pump plungers 36. In a manner to be described hereinafter, fuel chambers are filled with fuel from the metering shaft during the intake stroke of each plunger, and pump fuel into injection lines during the compression stroke of each plunger by Way of suitable fuel fiow channels in the metering shaft that connect each metering hole with an injection port 48. Within the engine idle speed range of operation, governor 54 will maintain the metering shaft in a desired axial position to deliver a predetermined schedule of fuel to each of the fuel injection lines. Depression of the accelerator pedal beyond the idle speed range will overcome the governor means and raise the metering shaft to change the schedule of fuel flow to the injection lines.

Turning now specifically to the construction of the metering shaft, the outer periphery or face of the metering shaft is provided with a number of recesses or cavities 62, 64, 66 and 68. The cavities are separated circumferentially and axially from each other by the intervening face portions of metering shaft 20 that sealingly engage the wall of bore 18. Each of the cavities extends both axially and circumferentially along a portion of the length of the metering shaft, and axially varies circumferentially in cross section, as shown. The recesses or cavities described above, in effect, constitute fuel flow channels in the face of the metering shaft.

The recesses or channels 62 and 66 each are connected via holes or bores 70 to a fuel transfer pump, not shown, that supplies the necessary quantity of fuel to satisfy the fuel pump requirements. The cavity or channel 64 is a fuel injection transfer cavity. It is connected to a helical channel 72 that aligns individually with each of the injection line holes 48 during rotation of shaft 20. Slightly downstream, i.e., circumferentially spaced from cavity 72, is the volume retraction channel or cavity 76. This is a helical channel that aligns its upper end with the injection line holes 48 subsequent to the holes aligning with channel 72, and simultaneously aligns its lower end with the metering holes 42 to spill a finite quantity of fuel back into a pump plunger cavity 40 when the plunger is on its intake stroke.

Volume retraction channel 76 also is connected at all times to the cavity 68, which is connected by a vertical channel 78, and a channel 80 to a chamber 82 formed in the metering shaft. The fuel under pressure in chamber 82 reacts against the shaft 20 in a manner urging the shaft away from the bore so as to balance the force of the high fuel pressure in the fuel injection line channel 72 that acts against the shaft bore 18 in the opposite direction.

Thus, it will be seen that channels 64 and 72 direct the flow of fuel from the pump plunger cavities 40 and metering holes 42 to the injection line holes 48 during one portion of rotation of the metering shaft; and that the recess or channel 76 constitutes a volume-retraction channel for the retraction of a finite volume of fuel from injection line holes 48 to the plunger cavities 40 during another portion of rotation of the metering shaft.

The cavities 62-68 formed in the metering shaft will be of an axial length such that they will always align with the metering holes 42 during the circumferential r0- tation of the metering shaft regardless of the axial position of the metering shaft due to movement of governor 54 or fuel regulator lever 60. The circumferential width of each cavity is predetermined so as to vary the quantity, time of initial injection, and duration of injection in accordance with the positions of the fuel regulator lever 60 and governor 54, to provide the proper schedule of fuel to the engine cylinders as a function of engine speed and load, etc. As can be seen, each cavity increases in circumferential width in an axial direction.

In operation, cavities 62 and 66 initially will be filled with fuel from the transfer ports 70. As the metering shaft 22 is rotated, say clockwise, by the engine, passage 66, for example, will initially align with a metering hole 42 and permit flow of fuel into one of the plunger cavities 40. The rotation of the metering shaft will be coordinated so that cavity 66 is cracked open to the metering hole 42 as the plunger is beginning its intake or downward stroke. As the plunger starts its upward or compression stroke, continued rotation of the metering shaft will cut off cavity 66 from hole 42 and begin to align one portion (depending upon the axial position of shaft 20) of the fuel injection transfer cavity or channel 64 with the plunger cavity 40 and metering hole 42. Fuel will then be forced into channel 64 and through the helical passage 72. Simultaneously, one of the injection line holes 48 will align with passage 72 and permit a charge of fuel to be injected into one of the lines 50. This injection will continue until the leftward edge of channel 64 closes metering hole 42, and passage 72 moves out of alignment with injection line hole 48.

Shortly thereafter, the volume retraction channel or passage 76 will align with the same injection line hole 48, and fuel will spill into the metering hole 42 of one of the plungers 36 that is about to commence its downward stroke. Continued rotation of shaft 20 will then misalign passage 76 with both injection line hole 48 and metering hole 42. Thus, a predetermined quantity or volume of fuel will have flowed from one injection line 50 through channel 76 into metering hole 42 and plunger chamber 40, retracting a finite volume of fuel from the injection line. The residual presure in the injection line will then have dropped to a value preventing after-injection.

The upward or downward axial movement of metering shaft 20 during any of the above cycles, will of course, merely vary the time of initial injection of and duration of injection of the fuel because of the varying tangetial widths of the fuel injection transfer cavity 64 and its angularity changes along its axial length.

From the foregoing, therefore, it will be clear that the invention provides a fuel injection pump assembly that eliminates the need for separate volume retraction delivery valves for each injection line by incorporting a volume retraction channel in the movable metering shaft. It will thus be seen that the fuel injection pump of the invention is more economical to manufacture and contains fewer parts than known similar types, and thereby provides a greater wearlife to the assembly.

While the invention has been illustrated and described in its preferred embodiment, it will be clear to those skilled in the art to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

What is claimed is:

1. In a fuel injection pump of the reciprocating plunger type having a central bore containing a rotatable metering shaft intermittently cooperating with individual ones of a plurality of fuel metering spill holes circumferentially spaced around the periphery of said bore and each connected to a chamber containing a plunger, the improvement comprising,

a plurality of circumferentially spaced fuel injection line ports each opening into said bore and connected to a separate fuel injection line,

first fuel channel means of predetermined circumferential width in said metering shaft individually connecting each of said metering holes in turn to separate one of said ports for a predetermined interval during one complete rotation of said shaft to supply fuel from said plungers to said injection lines during the compression stroke of the individual associated plungers, and volume-retraction channel means of predetermined circumferential width in said metering shaft circumferentially spaced from said first channel means and located after said first channel means with respect to the direction of rotation of said shaft,

said volume retraction channel means connecting each of said injection lines to a plunger chamber during the intake stroke of said plunger and subsequent to the disconnection of said latter injection line from said first channel means, to reduce the volume and pressure of the fuel in said latter injection line.

2. A fuel injection pump as in claim 1, said first channel means extending axially and circumferentially with respect to said shaft and varying circumferentially in width along its axial extent.

3. A fuel injection pump as in claim 1, said volumeretraction channel means extending axially and circumferentially with respect to the axis of said shaft and varying circumferentially in width along its axial extent.

4. A fuel injection pump as in claim 1, said fuel metering spill holes and injection line ports being axially spaced from each other and normally separated in a fuel flow sealing manner by the outer periphery of said shaft.

5. A fuel pump as in claim 1, said first channel means comprising a recess in the face of said shaft opening into the Wall of said bore.

6. A fuel pump as in claim 1, said channel means each comprising a recess in the face of said shaft normally closed by the wall of said bore.

7. A fuel pump as in claim 1, said shaft includingfurther fuel flow channel means connected at one end to a source of fuel and at the opposite end to said spill holes when aligned therewith during roatation of said shaft to supply fuel to said individual plunger chambers.

8. A fuel pump as in claim 1, said shaft including a fuel chamber opening into the wall of said bore and connected to said volume retraction chambers in a manner such that the pressure of the fuel exerts a force on said shaft tending to balance the side load on said bore exerted by the fuel in said channel means.

9. A fuel injection pump as in claim 2, said shaft being movable axially to vary the time of initial connection and duration of connection of said metering holes to injection lines.

10. A fuel pump as in claim 9, including internal combustion engine accelerator pedal means operatively connected to said shaft for moving said shaft axially in one direction in response to depression of said pedal from a normal position, and governor means operatively connected to said shaft for moving said shaft axially in the opposite direction in response to increases in shaft speed.

References Cited UNITED STATES PATENTS 2,357,563 9/ 1944 Truxell 103-173 2,417,137 3/1957 Smith.

2,428,408 l0/l947 Beeh l03l73 X 3,055,305 9/1962 Bostwick.

3,064,579 11/1962 Staege et al.

3,124,116 3/ 1964 Morris.

3,319,568 5/ 1967 Repko et al. 103-2 FRED C. MATTERN, 1a., Primary Examiner.

W. J. KRAUSS, Assistant Examiner. 

